For y= −log2x. a) Use transformations of the graphs of y=log2x and y=log3x o graph...

Step 1
a) Start from the graph of the parent function ${\displaystyle f\left(x\right)={\log }_{2}x}$.
As we can see the given function ${\displaystyle y=-{\log }_{2}x}$ can be expressed in terms of the parent function f as ${\displaystyle y=-f\left(x\right)}$
This indicates that the graph of the function ${\displaystyle y=-{\log }_{2}x}$ will be the same as the graph of the parent function ${\displaystyle f\left(x\right)={\log }_{2}x}$ reflected through the x-axis.
See the graphs in the picture below:

Step 2
b) The domain of the function ${\displaystyle y=-{\log }_{2}x}$ is the interval: ${\displaystyle (0,+\mathrm{\infty })}$
The range of the function ${\displaystyle y=-{\log }_{2}x}$ is the interval ${\displaystyle (-\mathrm{\infty },+\mathrm{\infty })}$
c) The vertical asymptote of the graph of this function is the line ${\displaystyle x=0}$